Re: query enhancement
- From: "fitzjarrell@xxxxxxx" <fitzjarrell@xxxxxxx>
- Date: Fri, 15 Jun 2007 10:44:42 -0700
On Jun 15, 12:22 pm, keeling <jkeelin...@xxxxxxxxx> wrote:
I am attempting to enhance a query so as to avoid a full table scan.
The query, as it now stands, tests for the presence of 'null' in one
column; the return of 1 or greater rows will satisfy my test,
therefore I'd like the query to stop after finding the first
occurrence of null. present query is as follows:
select count(*) from tableX where columnX = null.
Any suggestions would be greatly appreciated.
Sorry, that query won't work as nothing equals NULL; I expect your
count(*) will always be 0. You'd be better writing this:
select count(*) from tableX where columnX IS NULL;
which will produce an accurate count(*). You might try this:
select count(*)
from tableX
where exists (select 'x' from tableX where columnX is null);
Presuming you have an index this may produce an index fast full scan
access path rather than your full table scan.
It's a thought.
David Fitzjarrell
.
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